Getting ready to start rotating monitor setup

[epetti]

I've finally reached the point where I'm ready to start my rotating monitor setup for my cabinet.  I've got an LG 20" 4:3 monitor that's already on a swivel stand so I know it's well centered.  I was going to try DNA Dan's inspiring and very detailed setup here:

http://forum.arcadecontrols.com/index.php/topic,110471.0.html

but that changed directions a couple times and before I started I wanted to make sure that at least my shopping list for parts sounded right for making this thing.  Here's what I've got so far:

- lazy susan bearing, 3-4", such as found at vxb, but make sure that it's got clearance for the cable to pass through.
- MDF, particle, or choice of material for a 23" round mounting board and 24" base plate (downsized an inch from DNA Dan's to fit my cabinet slightly better.
- Screen door hinge or similar to force the wheel to stay on the turntable.
- Polulu motor controller (so many choices -- 7A to 30A which to pick? I assume 7A is sufficient.)
- USB A to Mini-B cable
- Polulu metal gearmotor (ranges from 19:1 to 131:1 gearbox, once again which one to pick?)
- Additional polulu supplies: wheel, crimp connectors, pins, bracket, hub.  Did I miss anything?
- Additional wood pieces for the 90 degree stops.
- Various screws to attach everything.

That seems like a complete shopping list based on the thread.  Am I missing anything?  Just about ready to dive off the deep end... 

And thank you in advance for going through all the trial and error to get to what seems like a fairly simple process at the end, including full HyperSpin setup.

[darthpaul]

Limit switches? How are you going to rotate it, will it be automated?

[epetti]

Sounded like the software that came with the polulu controller was able to detect a stop and stop the motor, so you didn't need a switch, just a stopper. That's the best of my understanding from the thread. I'm planning on rotating it by basically using a lazy Susan turned by a wheel powered by a motor, with physical stops, and have it driven automatically through Hyperspin and Autohotkey based on a list of which games are vertical.

[epetti]

Ah, just found this thread which gives me the exact shopping list I was looking for:

http://forum.arcadecontrols.com/index.php/topic,112424.0.html

[darthpaul]

That make life much simpler if the controller can do that.

[DaOld Man]

I have toyed with the idea of using a current sense circuit to detect when the motor "dead ends" against the mechanical stops, but havent created any real time circuits, although I dont think it would be too difficult.
My proposed circuit monitors a voltage drop across a low ohm resistor in series with the motor. If voltage across the resistor jumps up to a selectable level, the circuit outputs a signal that motor has reached its destination. (The motor stalls, shooting current up, voltage across resistor jumps up too. E=I*R)
There are some problems with this though.
The first I can think of is that it's not healthy for the motor to come to a dead head stop, it can generate heat in the motor and stress the windings. Also coming to a physical stop every time can put stress on the bearings of the motor and your rig.
Not to mention the stress of the increased current on the drive and the wiring.
Im also interested in how the controller senses that the motor has reached its destination.
Epetti, can you elaborate on it?

[epetti]

I hadn't gone into a deep dive of how it would work.  Reading through it again, I may have misinterpreted how DNADan's was working.  I got the impression that the control for detecting a stop was built into the controller that he ordered from polulu.  Reading through the info on the controller, though, it looks like just the wiring and controls for the limit switches are directly built into the controller, but you would still need limit switches.

Having said that, there are plenty of examples of safety mechanisms on existing commercial devices that stop and reverse when they detect impediment.  Seems like a solvable problem.  Just haven't put any thought into it.

[DaOld Man]

Bump.
Any progress?

[epetti]

Sorry I never looped back with this thread. Finished the cabinet about four months ago. Project thread is here:

http://forum.arcadecontrols.com/index.php?topic=131671

That thread includes links to the other posts I used as inspiration for the rotating part.

Never ended up doing an automated stopping mechanism. Just has two micro switches at 90 degrees that signal the motor to stop when they're hit. Works great.